Because with a 20mm f1.7 on a GF it may be worth it because of size.
When the Panasonic 20mm f1.7 first came out I owned a G1 and had already had bought a 28mm f2.8 manual focus legacy lens to play with. I wrote a blog post about it at the time having tried one in a shop and gone away to think about it. I wrote a post then subtitled do I really need one. That post could probably also have been subtitled instead: "will I see a benefit"...
Given that it was €400 I was a bit shy with parting with my money I felt at the time that having the kit 14-45 (quite a good lens really) and a OM28mm f2.8 I thought it wasn't worth it.
Later when the Sigma 30mm f2.8 came out I thought I'd try that out to compare with my OM28mm f2.8, expecting them to be quite similar. Which they were (see this link). I initially thought that the Sigma may work well on my GF (which I didn't have back when I first looked at the 20mm) but to be honest its physical size gave me nothing much to love about it over the 14-45. When used on my GH (an SLR-ALIKE camera) there was equally little benefit as the OM28 was optically quite equal at f2.8 and manual focus worked better for me when I was after critical focus anyway.
So how am I looking at this?
Essentially I'm interested in:
- differences in angle of view between the OM28 and the Pana 20
- shallow depth of field on the lenses
- clarity on the lenses
So whats it look like?
I like "normal lenses" for working at "normal" distances and taking "normal" sorts of shots (you know, not particularly wide, not particularly telephoto). With a f1.7 lens working outdoors in full sunlight will challenge the shutter speeds even at ISO 100, so I took a shot of my mate Bob working in his shed.
All images are taken with each lens "wide open"
Firstly the Panasonic 20mm
then the OM 28 taken from exactly the same spot.
I guess its pretty clear that the focal length difference which I identified in my 2010 blog post is still exactly what it was. To make that clearer here it is in this instance again:
the red frame in this shot is about what you get with the 28mm and the whole shot is of course taken with the 20mm.
So, some difference, but nothing which is staggeringly different. In some ways this sort of thing is what can easily be achieved with "zoom with your feet"
So in the shot below I moved back a bit and took the shot again to get a framing with the OM28mm equivalent to that of the 20mm (standing that bit closer)...
Open the images up in different windows and switch between them, I'm sure you'll agree that the character of the 28mm and 20mm are quite similar and the background relationships between them (caused by change of focal length and shifting position) are not specifically drastic.
Of course the background snuggles closer while Bob remains the same in the focal plane. Depth of Field is not significantly altered. So unless you have a specific plan it just may be that for things at "normal distances" the 20mm is a nicer tool in some ways. Like it does give you f1.7 vs f2.8 which could give you 100th of a sec VS 30th of a sec ... or enough to make a hand held shot sharper. These were all taken with a tripod.
So this begs the question of "can I crop the 20mm lens image back to equal the 28mm lens (or maybe just equal to a much more expensive 25mm)?
Well here is the 20mm cropped back to the view of the 28mm
Which is surprisingly similar to the original 28mm lens image.
So, what have we lost in details by cropping? Well that's a good question as the Panasonic 20mm lens should be a much sharper tool than the OM 28mm lens (designed for 35mm so many decades ago now) so lets have a look at the 100% pixels from a cropped 20mm upsized back to 4000pixels wide:
and the original capture of the OM28mm at 100% pixels
which is not too far apart and unless you were doing a very demanding print to put on a gallery (in which case you'd probably plan ahead better).
Also interesting is that the DoF of the 28mm @ f2.8 is almost the same as the DoF of the 20mm @ f1.7 when you factor in the changes in shooting distance.
The 20mm cropped and upsized shows that it does well and would do better if we were only cropping it to equal the Panasonic 25mm f1.4 field of view (of course that lens is bigger, brighter, more desirable and more expensive). I'm not sure I'd want that lens on my GF1 but it would be good on the GH...
As I was writing this
It occured to me that what I should also have done is to take a shot with the 20mm stepping closer to the subject rather than just with the 28 stepping back (to equalise the 28 to the 20). This would give the effect to be seen of the 20mm in closer from where the 28mm was taken from. Luckily we used a tape measure on the floor :-)
As the light had changed I took another set of two shots. So
The 28 taken from the same place as the first 28 shot was taken from:
Then the 20 stepping in a bit closer...
Same sorts of background / foreground perspective changes, but now that we're in closer the DoF from the f1.7 makes the background softer (check out the CH of the top row of the business card behind the screwdrivers).
As long as you're not shoving the camera in his face the facial distortions from trying to capture in too tight with a normal (making a portrait use of it) the differences between 20mm and 28mm are barely apparent.
To me the last shots clinched it for me, the 20mm with "zoom with your feet" is quite equivalent to the 28mm (and probably the 25mm too) and so I feel I've answered that question.
So, what'll I do ... I'm not sure. I happen to like this little lens, so I think that to do it credit I'll have to take some shots with it for a while and see.
Ultimately I think its not worth it to me on the GH body as it brings little advantage to me in its size. If the AF is not to be relied on for shallow DoF work (and picking focus right exactly where I want it to be) then its of reduced usefulness to me.
To me the question is now this;
will I be better served with a GF1 (still the best GF if you ask me) with this lens + 14mm + 0.79 wide adapter than I will be with selling it on again and just buying the 25mm f1.4?I could still buy a 14mm and a GF1 for less than the extra required to have bought a 25mm f1.4 over this lens.
Sure its not just a question of the lens and is it good enough as without doubt the Panasonic 20mm f1.7 is a great lens, it also happens to be a compact pancake lens and makes the GF camera actually achieve its potential of being compact.
All of which most of the newer micro43 cameras seem to fail at (with the exception of perhaps the GM).
Hope someone has found it interesting to see the Pana 20mm up against a legacy 28mm lens and also seen that the DoF difference between them is not only what calculations may have revealed.